Integrated Bulk and Spatial Proteomics of Castleman Disease: Molecular Signatures Across Subtypes and Compartmentalized Pathogenic Networks in iMCD-TAFRO.

Castleman disease (CD) represents a heterogeneous group of lymphoproliferative disorders, with the idiopathic multicentric CD subtype associated with TAFRO syndrome (iMCD-TAFRO) posing significant research challenges due to its severity and tissue scarcity. This study employed integrated bulk and spatial proteomics to characterize protein expression profiles in lymph node samples across clinical and pathological subtypes. Bulk proteomics revealed subtype-specific molecular signatures, including distinct protein profiles for hyaline vascular versus plasmacytic variants, systemic complement activation distinguishing iMCD from unicentric CD (UCD), and molecular evidence supporting the classification of iMCD-IPL as a distinct entity. Specifically, iMCD-TAFRO exhibited upregulation of angiogenesis drivers (PDGFRβ, NOTCH3), interferon signaling proteins (STAT1/ISG15), and fibrosis markers (COL3A1/LOXL1). Spatial proteomics, through laser capture microdissection of follicular and vascular niches, delineated compartmentalized pathogenesis in iMCD-TAFRO. Intrafollicular vessels showed enrichment of myofibroblast markers (ACTA2) and programmed cell death regulators (GSDMD, TFRC), while interfollicular regions displayed TGF-β/SMAD3-mediated upregulation of LOXL1 linked to fibrosis. Follicular zones demonstrated complement activation (CFHR1/CFHR2) and M2 macrophage infiltration. Our integrated approach delineates the molecular heterogeneity of CD, reveals spatially resolved pathogenic drivers in iMCD-TAFRO, and provides insights into its unique vascular-fibroinflammatory pathology, offering a foundation for advancing precision diagnostics and targeted therapies.